Rock drill



Aug. 2, 1955 H. JESCHKE ROCK DRILL Filed May 8, 1951 l I .P I! 'l l BY 446m, gj/

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States Patent Ofiice 2,714,371) Patented Aug. 2, 1955 ROCK DRILL Herbert Jeschke, Duisburg, Germany Application May 8, 1951, Serial No. 225,102 Claims priority, application Germany May 13, 19511 4 Claims. (Cl. 121-15) to the product of the square of the diameter of the cylinder and of the stroke, i. e., the cylinder volume.

Drills of high capacity and low drill stress have, therefore, short strokes. This construction leads to difficulties which increase as the stroke shortens.

It is an object of my invention provide a rock drill of high capacity and moderate drill stress, that is, a drill having a high number of strokes per minutes at moderate impact. This is achieved by providing each of two sets of pistons and cylinders, which in a known manner are joined to two piston rods that alternatingly, hit a connecting piece acting on the drill shank, with a special control mechanism, one of which is pneumatically acting upon the other to guarantee the uniform alternation of the strokes.

To the accomplishment of the foregoing and other objects which will hereinafter appear, my invention consists in the apparatus elements and their relation one to the other, as hereinafter are more particularly described in the specification and sought to be defined in the claims. The specification is accompanied by a drawing in which Fig. 1 illustrates schematically an embodiment of my invention;

Fig. 2 is a section taken in the plane of the line 2-2 of Fig. l, drawn to enlarged scale; and

Fig. 3 is a graph illustrating the operation of the two pistons of the rock drill shown.

Referring to the drawing, especially Fig. 1, 1 is the housing of the two cylinders 3 and 4 which are divided by the circular wall 2. The two pistons are designated 5 and 6, respectively. There is a piston rod 7 which is hollow, and a piston rod 8 is located in the bore of the rod 7. Both rods serve to transmit the striking motion. They contact the connecting piece 9 which in turn acts on the shank of the boring rod 11. By means of a motor 12 located on the cover of the hammer housing, the drill is turned when in operation. Air inlets in the cylinders 3 and 4 are designated 14, 15 and 16, 17, respectively. Air entering at 18 and approaching the inlets 14, 15, 16, 17 through the channels 19 is controlled by flapper valves 20 and 21. The air outlets in the cylinders 3 and 4 are marked 22 and 23. A channel 24 connects both cylinder spaces and serves to secure uniform alternate operation of the working pistons 5 and 6, as will be explained below. The air entering at 18 is distributed over the two flapper valves 20 and 21 in either of the two channel arms 19 which direct the compressed air to the cylinder spaces 3 and 4 in such a way that the air enters alternatingly through 14, 17 and 15, 16 whereby the pistons are alternatingly pushed forward and backward. T 0 start the hammer in the proper rhythm, the flapper valves may be held under light spring tension.

Considering, for instance, the operation of the piston 5, with this piston being at the start of the forward stroke,

, fresh air enters through the air inlet 14 and drives the A 1 the intervals between strokes being equal.

piston forward, that is, to the right. While the piston moves forward, it first closes and then opens the air outlet 22, and it also compresses the air in front. Before the piston rod 8 strikes against the member 9, air from behind the piston is permitted to escape through the outlet 22 to the atmosphere, thus causing a rapid drop in pressure behind the piston, and a decrease of the pressure upon the corresponding (left-hand) side of the valve 20. At the same time, the pressure exerted upon the other (right-hand) side of the flapper valve 20, due to the compression of the air in front of the piston, increases and reverses the valve 20. Now, the valve admits fresh air to the front portion of the cylinder space 3, starting the back stroke of the piston. During this backward movement, air escapes through 22, and compression of air in the rear of the space 3 takes place. Due to the rapid changes of the direction of the piston movements and the correspondingly rapid change of the locations of the pressure application upon the valve 26), the latter performs a flapping motion.

The height and the pistons of the two rams are designed to carry out theoretically the same number of strokes per minute. The two mechanisms being independent of each other, they will actually work without a well defined rhythm and will approximately alternate, To obtain a rhythmic operation which is often desirable, one ram 6, 7 according to my invention is to run slightly slower and its movement is to be accelerated by the influence of the other ram. It is furthermore required that the rams hit alternatingly in uniform succession, and it is important to have one ram influence the second ram, which by itself would run somewhat slower, in such a way that the latter is forced to accept the rhythm of the first ram. This is made possible according to my invention by providing a transfer channel 24 at a suitable place between the cylinders 3 and 4. To prevent air flow in the wrong direction, a check valve 25 is provided in the channel 24 (see Fig. 2). The orifices of the channel are located in the cylinders 3 and 4 at the far ends from the drill, and the orifice in the cylinder 4 is located beyond the travel of the piston. The orifice in the cylinder 3 is governed by the piston 5 in such a fashion that the compressed air entering the rear compartment of the cylinder 4 advances the reversal of the slightly retarded piston 6, thereby reducing the stroke of the piston 6 and thus maintaining a uniform rhythm.

From Fig. 2 it will be seen that the transfer channel or passage 24 and the check valve 25 provided therein allows air to flow only in the direction indicated by the arrow, namely, from the cylinder 3 to the portion 26 of the cylinder 4.

The operation and control of the two pistons, according to my invention, is illustrated by curves plotted on coordinates representing the course of the piston stroke s and time t (see Fig. 3). Curve A represents the stroke of the piston 5, the point a being the impact of the piston rod upon the member 9. Curve B represents the stroke of the piston 6. Piston 6 is designed to move somewhat slower than piston 5, which can be accomplished, for instance, by giving the piston 6 a greater Weight. Without the transfer channel 24, the pistons 5 and 6 would be independent from each other, and the heavier piston would not strike in uniformity with the piston 5. In Fig. 3, 12 is the time of the slower moving piston 6, which time is longer than t1, the time of the piston 5 (the greater length is shown in exaggerated form).

With my transfer channel, however, a certain amount of compressed air, whenever needed, is allowed to flow from the cylinder space 3 into the cylinder space 4, with the result that during the backward movement of the piston 6 the pressure in the space 26 increases more rapidly and operates as a stronger brake, thus shortening the stroke of the piston 6. In such cases, the piston 6 carries out a movement which is represented by the curve C, whereby ts equals t1 so that both pistons will perform the same number of strokes in a uniform alternate succession. The piston 5 controls the opening 27 to the channel 24 and regulates the rhythm of the piston 6. As long as both pistons keep time in moving, the channel 24 will be ineffective since the pressure in the space 26 will not be smaller than that in the space 3 at the time the piston 5 opens the port 27. With the piston 6 moving out of time, the effect of the air supplied through the passage 24 will be greater in proportion as the piston 6 is out of time. It will be understood that any of the pistons may control the other one. It is, however, necessary that the regulating piston moves somewhat faster.

My improved design of a rock drill equipped with two rams afiords not only double capacity, as compared to a single cylinder hammer of conventional construction, but also means for an economical realization of a rock drill equipped with twin rams, the two cylinders and pistons of which are combined according to a known suggestion, in analogy to a two-cylinder steam engine, to a compound machine which thus is to work with a single control mechanism. The apparatus of this invention is particularly suitable for use with the known portable large size frames which usually serve to support several rock drill hammers of generally heavy construction.

It will be apparent that while I have shown and described my invention in a preferred form, many changes and modifications may be made without departing from the spirit of the invention defined in the claims. Thus, it will be understood that the desired efiect can be achieved by other means than the transfer channel shown It is, however, essential that each piston has a control With the use of flapper valves of 1. Fluid-actuated rock drilling machine, especially for use with drills of high hardness, comprising two separate cylinders coaxially arranged one behind the other, a piston movably arranged in each cylinder, a piston rod connected to each piston, one piston rod being movably contained within the other piston rod and passing through the piston of the latter rod, each set of cylinder and piston forming a separate ram, both pistons being adapted to act upon the same member, a channel conducting compressed driving fluid to each of the cylinders, a valve mechanism in each of the pressure fluid channels to control the pressure fluid supply individually and to cause the pistons to move alternatingly, and a channel connecting the two cylinders to guide driving fluid from one of the cylinders into the other to pneumatically influence the piston of said other cylinder to secure uniform alternation of the strokes.

2. In the machine according to claim 1, each valve mechanism including a flapper valve, the flapper valves being controlled by the pressure both forwardly and rearwardly of the moving pistons and admitting air to,the cylinders for alternatingly opposed movements of the pistons, and resilient means to hold the flapper valves during idle periods of the machine in a position so as to cause proper alternation of the pistons at the start of the machine.

3. In the machine according to claim 1, one of the pistons being adapted for movements slower than those of the other piston, the slower moving piston being arranged as the piston to be influenced, the faster moving piston being the influencing piston, the channel connecting the two cylinders guiding compressed driving fluid from the cylinder of the faster moving piston into the cylinder of the slower moving piston, the port of the channel in the cylinder of the faster moving piston being controlled by the latter piston, a check valve being located in the channel to prevent the flow of driving fluid in the opposite direction.

4. In the machine according to claim 3, the port of the said channel in the cylinder of the slower moving piston being at the far end from the drill beyond the travel of the slower moving piston, the conduction of said compressed driving fluid through the channel being controlled by the movement of the slower moving piston.

References Cited in the file of this patent UNITED STATES PATENTS 393,461 Donald Nov. 27, 1888 592,116 Johnson Oct. 19, 1897 1,874,130 Smickle Aug. 30, 1932 1,970,433 Schabarum Aug. 14, 1934 1,976,524 Sgonina Oct. 9, 1934 

